Wind energy systems are traditionally anchored in offshore use in the form of single-post foundations on the ocean bottom. Furthermore, tripod foundations are known in which the foot of the wind energy system comprises three legs that run out from each other in a tetrahedral shape and are anchored on the ocean bottom. Moreover, foundations with jackets are known in oil platforms that have a framework construction exposed primarily to stresses of traction and pressure.
It must be taken into account, especially in offshore wind energy system parks, that the hub height of the individual wind energy systems above the ocean surface should be approximately the same for optical reasons on the one hand. On the other hand, for example, the boat docking areas can be built at the same height of the main construction in all wind energy systems by virtue of the same penetration height at the level of the ocean surface. The natural oscillation behavior of the system is less a function of the height above the ocean surface than it is of the height above the ocean bottom. Thus, the natural oscillation behavior of wind energy systems must be recalculated for each system every time that a plurality of systems is erected at different ocean depths. The obtaining of an approximately equal hub height above the ocean surface is complex in the case of such foundations because the length of the tripod or that of the jacket must be adapted in its entirety to the erection site.
WO 03/080939 A1 teaches a foundation for an offshore wind energy system comprising a suction foot to which the tower of the wind energy system is fastened with lateral struts.
DE 201 00 588 U1 discloses an offshore wind energy system comprising feet that can be flooded with water. The foot of the wind energy system can be lowered in a controlled manner by the flooding of the feet.
U.S. Pat. No. 4,590,718 teaches the foundation of an onshore wind energy system. The weight of the wind energy system is transmitted via a tower onto the ground and lateral, height-adjustable feet stabilize the entire construction.
JP 2003028046 A describes a foundation for an offshore wind energy system comprising feet with different heights, a few of which feet are arranged above the ocean surface and a few below the ocean surface.